Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 261754
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1054 AM MST Sat Nov 26 2016

.SHORT TERM...(Today through Sunday)
Issued at 250 AM MST Sat Nov 26 2016

One last day of pleasant weather on tap before everything changes.
Another cool start to the day will then bring mostly sunny skies
to the region though a few high clouds can`t be ruled out. As the
day progresses, clouds will be on the increase over the Four
Corners and San Juans thanks to the next system. High temperatures
will inch up a few degrees from seen yesterday but all in all, a
very similar day to yesterday.

By late tonight, the next storm system will start to affect the
area. First, a deep trough will be coming ashore over the West
Coast and ahead of it, winds will pick up thanks to the jet stream
and also a tightening gradient. Southwesterly flow will also tap
into moisture off the Pacific giving the trough something to work
with. Forecast models have been very consistent with precipitation
starting right around midnight tomorrow for the San Juans before
spreading northward with some showers possible before then. By
daybreak, precipitation will have reached the central mountains
and then the northern mountains a few hours later. Snow for the
mountains looks to be a no-brainer but the valleys will be tricky.
A few inches of snow for Cortez, Durango, and Pagosa Springs
certainly look possible but if temperatures are just a hair too
warm, rain will fall. This will be something later shifts will
need to keep an eye on. The Grand Valley and northern valleys will
also need to be watched as the colder air filters in allowing snow
to reach lower elevations.

A few other concerns is the nature of this system and that being
several distinct pieces of energy moving overhead. These pieces of
energy will keep precipitation going through Tuesday, if not
beyond. Of course, snow will not fall the entire time for the
mountains as there will be lulls, breaks in the clouds, and stops
in precipitation but this will be rather short-lived as the next
disturbance moves through. Another concern will be gusty winds
above 9,000 feet that will cause blowing snow that may drop
visibilities to near zero at times. Snow amounts? Skiers can
rejoice as the mountains will likely see anywhere from 10 to maybe
even 20 inches of new snow before all is said and done.

So for this mornings package, all watches have been upgraded to
warnings and also added an advisory for Zone 3 as Douglas Pass
will certainly see some impacts from the snowfall. As mentioned
above, snow will begin over the San Juans late tonight and by
Sunday morning, snow will have reached Vail Pass and a few areas
north. For those individuals debating on when to drive home after
the holiday, conditions will be perfect today and deteriorate
rapidly overnight. If possible, leave today because by Sunday
morning, it`ll be a mess out there.

.LONG TERM...(Sunday through Friday)
Issued at 245 PM MST Fri Nov 25 2016

As the initial trough exits northeast Sunday afternoon, the worst
of the heavy snow and wind will be over. However, a second trough
will drop through UT and head over NM Sunday night. Weak lift but
northwest orographic flow will persist over the region continuing
periods of light snow that will impact mainly the mountains and
adjacent windward high valleys. Colder air will filter in as well
setting the stage for a prolonged period of more winter-like
temperatures. Snowfall amounts for the Colorado mountains and
mountains of southeast Utah will likely be fairly hefty...1 to 2
feet through Monday. This combined with the expected impacts from
strong winds and blowing snow further supported the issuance of a
Winter Storm Watch. Blizzard conditions certainly possible in the
San Juan mountains above 9000 feet with travel over mountain
passes seriously impacted if not temporarily shut down. Will be
messaging this potential for those traveling home from the holiday
festivities.

A third shortwave trough in the northwest flow aloft will move
over the region Monday night...followed by yet another weaker
trough Tuesday night. Again...this keeps the unsettled showery
weather pattern over the region going...affecting mainly the
favored northwest-facing terrain and high peaks.

Models showing some differences by late next week with northern
stream trough potentially digging south and cutting off over the
Great Basin or Desert Southwest. However there is good agreement
all week on the general upper level trough pattern over the
western CONUS. This favors below normal temperatures so have
hedged toward the colder side of the model guidance.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1054 AM MST Sat Nov 26 2016

Sunny skies with VFR conditions will prevail through much of the
day today. High clouds will begin to invade from the south this
evening with rain and snow showers increasing after 06z Sunday.
Winds will also increase from the southwest as well at the
mountain TAF sites with gusts to 40 kt at KTEX and higher among
the ridges. Ceilings and visibilities will lower due to increasing
rain and snow with precipitation becoming widespread at all TAF
sites by 12z Sunday and beyond. Winds will cause areas of blowing
snow for mountain TAF sites and any southern valleys that switch
over to snow Sunday morning, including KDRO. Mountains will be
frequently obscured Sunday morning and beyond due to heavy snow
and blowing snow.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Storm Warning from midnight tonight to 6 AM MST Monday
     for COZ012-018-019.

     Winter Storm Warning from 6 AM Sunday to 6 AM MST Tuesday for
     COZ004-009-010-013.

     Winter Weather Advisory from 6 AM Sunday to 6 AM MST Monday for
     COZ003.

UT...Winter Storm Warning from midnight tonight to 6 AM MST Monday
     for UTZ028.

&&

$$

SHORT TERM...TGR
LONG TERM...BEN
AVIATION...MDA



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